Vacuum plates

[Raskins]

I am working with copper plate 1.5" x 6" x 16" and would like to cut a profile and some pockets on my cnc mill. Has anyone tried to use a vacuum plate as a holding fixture? There are a few angles that need to be cut this is why i was thinking of vacuum so i can do it once with no clamps.

Thanks
Ken

[Rekd]

I use vacuum all the time. If your mat'l is flat on the 'down' face, you should be fine, just take light cuts.

'Rekd

[DAB_Design]

wow, look at me drag up all the old posts today.

We use alot of vacuum set ups where I work. A couple of pointers...

We use various types of rubber seals on our vacuum fixtures. Most common is .250 round. Mill a groove about .200 deep x .250 wide (for .250 round) inside the periphery of your part, and around any cutouts/holes. How far away from the part depends on the finished thicknesses (the thinner the finish thickness, the closer you want the seal).

Also, mill a small groove, at least .020 deep just inside the seal. Usually we just use either a .250 Ballnose or a .125R 7degree die sink for this. And add a "hatch" groove all over inside the seal, all the way out to the outside .020 deep groove. Make sure you intersect the groove at some point with the vacuum 'port'.

This will insure that you have consistant vacuum all over the part.

I do have to say that there are NO vacuum setups we run that do not also use hold down bolts/toe clamps. But as Rekd states, if you take small enough cuts, it may not be an issue.

The largest part we use vacuum on is an outer skin (vertical stabilizer) for a rather large aircraft. Finished part is about 16 x 40........feet(just a guesstimate)